Heretofore, magnetic disk drives have been employed so that information can be written to or read from magnetic recording media. For this purpose, the space between a magnetic head and a magnetic recording medium is usually maintained at a very small value, say between 0.2 and 0.3 .mu.m. If the head makes frictional contact or collides with the recording medium, they will be worn down or get damaged. To avoid this undesirable phenomenon, a floating head slider carrying a magnetic head is used. In particular, because of a speed difference between the slider and the surface of the recording medium a hydrodynamic floating force is produced in the gap between them to maintain the minute space between them.
However, when the magnetic recording medium is stopped, the aforementioned hydrodynamic floating force is not produced and, therefore, the slider is in contact with the medium and locked. Since the surfaces of the slider and of the medium are fabricated quite accurately, the slider may be attracted to the medium when they are at rest or stopped as described above. If the slider is attracted to the medium in this way, a rather large torque is needed to start or stop the medium. Consequently, it may become impossible to start the medium, or the head makes a frictional contact with the medium, damaging the contact surfaces. As a result, they can no longer be used. In this way, various problems are caused.
The means normally adopted to solve the above-described problems is to form microscopic grooves called a texture on the surface of the magnetic recording medium or to make the surface of the medium uneven. If the slider is brought to a stop on the medium, the slider is prevented from being attracted to the medium although the smooth surfaces actually come in contact with each other.
A known method of forming the texture described above is to etch pits or holes in random directions. A more common method consists in rotating a substrate for a magnetic recording medium and pressing an abrasive tape against the surface of the substrate by a pair of pressure rolls made from a resilient material such as rubber. Another common method is to press a disklike abrasive rotary member against the surface of the substrate. The obtained texture assumes either of two patterns. In one pattern, grooves are concentric about the center of rotation of the substrate. In another pattern, grooves intersect the circumferential direction of the substrate at an angle .theta. that is not constant. These two patterns are illustrated in FIGS. 5 (a) and (b), respectively. In FIG. 5(a), the grooves 1 in the texture are concentric. In FIG. 5(b), the grooves 1 in the texture cross the circumferential direction at angle .theta..
The prior art pattern of the texture on the substrate has been studied very little. The principle of the prior art method relies only on formation of grooves or on making the surface uneven. Therefore, if a desired texture is actually formed on the surface of the substrate, the intended decrease in the friction coefficient between the surface of the substrate and the magnetic head is not expected when they are used in practice. Consequently, the contact start and stop (CSS) characteristics and other characteristics of the magnetic recording medium are poor. In some methods, the roughness of the texture is limited within a certain range, but the angle .theta. at which each groove in the texture intersects the circumferential direction is by no means taken into account. This angle is hereinafter referred to as the intersection angle. For this reason, the CSS characteristics such as the friction coefficient on the surface vary greatly among fabricated magnetic recording media. Hence, the recording media have neither sufficient durability nor sufficient reliability.
In recent years, magnetic recording media have been required to have higher recording density and larger capacity. Therefore, it is necessary to greatly enhance the accuracy with which the substrate is machined. In addition, it is necessary that the pattern of the texture be made as optimal as possible to improve the CSS characteristics.
The present invention is intended to solve the foregoing problems with the prior art techniques. It is an object of the invention to provide a magnetic recording medium having a substrate on which a texture is created in a given pattern, thereby exhibiting reliable and excellent CSS characteristics.